Purpose The purpose of this paper is to investigate surroundings for transfer film formation and removal, the effect of the transfer film formation on friction coefficients, the effect of four different abrasive components, ZrO2, ZrSiO4, Al2O3 and Fe3O4, on transfer film formation and the effect of lubricating component MoS2 on transfer film formation and friction coefficients. Design/methodology/approach Two different MoS2 contents of 5.5 and 8.5 per cent were added to friction materials with no MoS2 content, which have four different abrasive components, ZrO2, ZrSiO4, Al2O3, Fe3O4. Friction tests composed of three different stages were conducted for those materials, and the friction surfaces of the counterpart disks were examined by scanning electron microscopy (SEM) to access the formation of transfer film at each stage. Findings For the transfer film formation, high temperature was a prerequisite, but the magnitude of deceleration rate was not important. The effect of the transfer film formation was to reduce the friction coefficients for most friction materials. Friction coefficients of materials which contain lubricating component MoS2 were higher than those which contain no MoS2 for most friction materials. The effect of the lubricating component MoS2 was to suppress the formation of transfer film, thus resulting in increase in friction coefficients. Research limitations/implications The transfer film was rather thin, with thickness of 1-2 µm for most friction materials. That hindered the examination of mechanical properties of the transfer film, such as hardness. Practical implications This research explained the surroundings for transfer film formation, and its effect on friction coefficients. The research suggests to suppress the formation of transfer film to make friction materials with high friction coefficient, and the lubricating component MoS2 can be used for the purpose. Social implications Development of high-friction-brake materials conventionally depends on the use of strong abrasive components, which may induce attacking of counterpart disks. The enhancement of friction coefficients with addition of MoS2 content is expected to open a new prospect in development of high-performance friction materials, which can be applicable to brake pads for racing cars. Originality/value The study is in pursuit of the transfer film formation in successive friction stages, which revealed the conditions for transfer film generation and removal. Specimen preparation for SEM observation of cross section of friction surface was painstaking to not damage the developed friction surface. The study revealed the effect of different abrasive components on transfer film formation and the effect of lubrication contents of MoS2 on transfer film formation and friction coefficients.
Purpose This paper aims to investigate the temperature dependence of transfer film formation and friction coefficients in NAO friction materials with four different abrasive components, ZrO2, ZrSiO4, Al2O3 and Fe3O4. Design/methodology/approach 8.5% SnS2 was added as a lubricating component to friction materials. Friction tests comprised 100 times of consecutive braking application for each friction material under constant temperature of 300°C, 400°C, 500°C and 600°C. After the friction tests, the friction surfaces of the counterpart disks were examined by scanning electron microscope to access the formation of transfer film. Findings Coefficients of friction depended on not only friction temperature but also friction history which is related to development of transfer film. The effect of the transfer film formation was to reduce the friction coefficients for most friction materials. Quantities of the transfer film formation varied with friction materials; at low temperature below 400° the transfer film formation was most active in the Fe3O4 materials, while at 600° it was the most active in the Al2O3 material. The effect of the lubricating component SnS2 was to suppress the formation of transfer film, thus enhancing friction coefficients. Social implications The enhancement of friction coefficients with addition of small amount of lubricating components such as SnS2 is expected to open a new approach in developing high performance-brake pads. Originality/value Temperature was the controlling parameter in the present test. Under these test modes, transfer film could be fully developed to access the role of the transfer film. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-10-2019-0427/
PurposeThe purpose of this paper is to investigate the friction coefficients of aramid and acrylic fibers on brake pads.Design/methodology/approachFiber components used in the present pads are aramid and acrylic fibers, respectively, while keeping other components, such as binders, lubricants, abrasives, fillers the same. Disk FC25 and disk FC17 are used for rotor rubbing test to investigate the friction coefficients with brake pads. The pads are tested by 1/5 scale brake dynamometer, and test mode is modified JASO C406‐P1. The results are analyzed with the friction coefficient and the temperature, transfer film, roughness, and photomicrograph of worn surface on rotors.FindingsThe friction coefficient was mainly determined by the pad material rather than the rotor material, and pads made of aramid fiber had high‐friction coefficient, while pads made of acrylic fiber had low‐friction coefficient, especially under high temperature. Temperature change during braking process was directly related to the initial speed only, and was indifferent to materials or decelerations imposed. In the fade test, the reversal of friction coefficients between the aramid fiber and acrylic fiber pads is determined by the amount of remained amount of respective fiber above 520°C.Originality/valueEffect of different fiber components, aramid and acrylic fibers, on friction characteristics of pad is sought. Reversal of friction coefficients is determined by the thermal stability of fibers used for pads.
Residual stress and texture in poly-SiC films grown by low-pressure organometallic chemical-vapor deposition Diamond films were grown over Si substrate at 1223 K by the hot filament chemical vapor deposition ͑CVD͒ method using CH 4 /H 2 gas mixtures ͑1%, 2%, 3% CH 4 ,) and the intrinsic stresses in the film were deduced using the ex situ curvature method. After subtracting the curvature change during the cooling process, average stresses in the film during the CVD process, ͗ f ͘, were calculated using the elastic/plastic analysis which treated the creep deformation of the substrate. The intrinsic stress kept increasing during the CVD process and was generally several times larger than the ͗ f ͘ which tended to saturate around the film thickness (t f ) of 10 m. For thicker films, substrate creep became significant and the substrate stress was substantially relaxed by creep. Fraction of the creep strain with respect to the total strain at the film-substrate interface was around ϳ1/3 when t f ϳ10 m, and increased as large as 2/3 during the film deposition. The intrinsic stress was believed to arise from the grain growth during the CVD process, because the stress deduced from the actual grain size measurements agreed reasonably with calculated values from the above analysis. Later, the diamond film layer was removed by O 2 electron cyclotron resonance etching, and the remaining curvatures of the substrate were compared with those deduced from the elastic/ plastic analysis. Residual stresses in the substrate after the film removal were tensile near the interface and the substrate bottom but compressive in the middle.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.